Virginia state Sen. Joseph V. Gartlan was a little stunned when a lobbyist told him he had voted against a resolution banning official government meetings in discriminatory clubs.

"I didn't think I had done that," said the perplexed Fairfax County Democrat, who promptly called the committee clerk to switch a vote that had been cast incorrectly in his absence--by proxy.

Sen. Peter K. Babalas (D-Norfolk) was no less surprised when the Senate calendar showed him voting in committee for a piece of landlord-tenant legislation to which, he explained later, he was thoroughly opposed. In his case, the mistakenly cast proxy vote was corrected on the floor of the Senate.

Such are the risks of having legislators vote for each other in committee, a system allowed in the 40-member Virginia Senate although not in the 100-member House of Delegates. It is not unusual for senators to find their proxy votes incorrectly cast by a colleague, or not cast at all. But because Virginia's senators each sit on three 15-member committees, some of which inevitably meet at the same time, the errors of proxy voting are tolerated.

"It has the potential for embarrassment and it also has the tendency to produce bad results," said Sen. Dudley J. Emick (D-Botetourt), who this week had to ask the Senate clerk to record him in favor of a slew of honorific resolutions. Emick had left his proxy in the Rules Committee with another senator who, in turn, had left his proxy and Emick's with a third senator who inadvertently forgot to record Emick in favor of such measures as a resolution honoring Redskins star Mark Mosley.

The proxy system adds another dimension to the prevailing confusion of Virginia's legislative process, befuddling lawmakers and lobbyists alike. It also has the effect, some complain, of devaluing the purpose of public hearings and debates.

"Sometimes you can't tell what the real vote is, because there are so many proxies floating around," said Judy Goldberg, lobbyist for the American Civil Liberties Union.

Still, things have come a long way since the days when committee chairmen could walk into meetings with pocketfuls of proxies. Under Senate rules adopted 10 years ago, a proxy vote can only be cast if the senator shows up at the start of the committee meeting and delivers a signed form to the clerk and to another senator.

"The first couple of years I was down here, I was strongly against proxy voting because I was convinced it reinforced a chairman's ability to control a committee," said Sen. Wiley F. Mitchell (R-Alexandria), whose first piece of legislation in 1976 was doomed when a committee chairman cast seven votes against it--only one of them his.

Since the tightening of the rules, most senators agree that problems can be avoided by leaving careful instructions on the proxy form. But many are apt to place their trust in their colleagues. "We pretty much know each other's philosophies," said Babalas. And, given the complexity of some legislation and the unpredictability of bill-altering amendments, some say that mistakes are inevitable.

Last year Sen. Charles J. Colgan (D-Prince William) left his proxy with Finance Committee Chairman Sen. Edward E. Willey (D-Richmond), only to find that a bill he vehemently opposed was released to the floor on a unanimous vote. When the error was noted, the bill went back to committee, where Colgan engineered its death.

"It happens all the time," said Colgan. "I always leave my proxy with the chairman and, hopefully, he votes me right. If he doesn't I can always get up on the floor and change it."

Defenders of the system argue that without proxy voting the senators, torn between sometimes as many as four committee meetings, would have to abdicate their responsibility to vote on certain measures. The problem has been particularly acute during the final weeks of a session, when senators are defending their own bills before House committees while House bills are being heard in theirs.

"Friday is the day I go bonkers," said Gartlan, who on the Friday that the rules committee killed the resolution on discriminatory clubs had simultaneous meetings in the Senate Rehabilitation and Social Services committees. "I literally have to be three or more places at once."

Many senators insist that their system is preferable to the House where, without proxies and because of scheduling conflicts, bills often are defeated by only a few committee members.

"They the delegates get bills coming out of 20-member committees on a 5-to-3 vote," noted Senate Majority Leader Hunter B. Andrews (D-Hampton) "Ours is a better system."

But the House has never had proxy voting, which is the way many of its members want to keep it.

"That has always been the custom in the House and it's not going to change," said House Speaker A.L. Philpott (D-Henry). "I think if you are going to vote, you should be there and if you're not going to be there, how can you vote?"